This invention relates to hydrogen peroxide destroying compositions, and to methods of making and using the same, which are useful to decrease the concentration of, or even substantially eliminate, hydrogen peroxide present in a liquid medium. More particularly, the invention relates to such compositions, and methods for making and using such compositions, useful in destroying residual hydrogen peroxide present in a liquid aqueous medium containing a contact lens which has been disinfected by the action of hydrogen peroxide and preferably cleaned by enzymatic action.
Contact lenses should be periodically cleaned and disinfected by the user to prevent infection or other deleterious effects on ocular health which may be associated with contact lens wear. Currently, there are several different conventional systems and methods which enable the user to clean and disinfect their contact lenses between wearing times. These conventional cleaning and disinfection systems can be divided into "hot" and "cold" systems. Hot systems require the use of heat to disinfect the contact lenses, whereas cold systems use chemical disinfectants at ambient temperatures to disinfect the lenses.
Within the realm of cold disinfection systems are hydrogen peroxide disinfection systems. Disinfecting hydrogen peroxide solutions are effective to kill the bacteria and fungi which may contaminate contact lenses. However, residual hydrogen peroxide on a disinfected contact lens may cause irritation, burning or trauma to the eye unless this hydrogen peroxide is destroyed, i.e., decomposed, neutralized, inactivated or chemically reduced. Therefore, the destruction of the residua hydrogen peroxide in the liquid medium containing the disinfected contact lens is needed to enable safe and comfortable wear of the disinfected contact lens.
Contact lenses can be cleaned by enzymatic action. For example, Huth, et al U.S. Pat. RE. 32,672 discloses the simultaneous cleaning and disinfecting of contact lenses by a method which comprises contacting the lenses with a solution comprising a disinfecting amount of peroxide and an effective amount of peroxide-active proteolytic enzyme for a time sufficient to remove substantially all protein accretions and to disinfect the lenses. This patent further discloses that catalases, organic enzymes which catalyze the degradation of peroxides, can be incorporated into tablets and powders, particularly in time-release form. Both the proteolytic enzyme and the catalase should have high activity to provide a highly effective degree of cleaning and peroxide degradation, respectively.
Associated with the problem of hydrogen peroxide destruction in contact lens disinfection systems are the problems of easy use and user compliance. To enhance user compliance and ease of use, several efforts have focused on one-step disinfection and hydrogen peroxide destruction. In this regard, various time release tablets containing a core tablet and a totally soluble or insoluble coating have been suggested.
Schafer et al European Patent Application 86-109,361.5 discloses a hydrogen peroxide neutralizer tablet covered with a water-soluble coating to delay the dissolution of the tablet. The coating is applied by conventional procedures such as by spraying on a film in coating pans, by fluidized bed methods, or in closed systems. This publication discloses the use of various soluble polymers, such as cellulose ethers, which include suitable polyhydric alcohols to control the timed release as a coating for the neutralizer tablet.
Kaspar et al U.S. Pat. No. 4,568,517 discloses a one step contact lens disinfecting process which involves hydrogen peroxide and a neutralizer having a hydrogen peroxide neutralizing compound in tablet or particle form and a coating encasing the tablet or particles which acts as a delayed release coating. Among the hydrogen peroxide neutralizing compounds disclosed are peroxidase/catalase enzymes. The coating may be made of organically modified cellulose, such as hydroxypropylmethyl cellulose, ethyl cellulose, cellulose acetate phthalate and hydroxypropyl cellulose. The neutralizer can be a coated tablet prepared by spraying an ethanol or acetone solution of the coating material onto a tablet containing the hydrogen peroxide neutralizing compound. The solvent is then evaporated leaving the coating. The use of purely organic solvents tends to produce non-uniform coatings with delayed release characteristics which are not totally satisfactory. In addition, certain organic solvents, such as alcohols, have an adverse effect on the activity of certain of the cleaning enzymes, discussed previously. The use of water as the solvent can have adverse effects on the hydrogen peroxide neutralizing compound, in particular catalase enzyme. It would be advantageous to provide a new solvent system for coating such hydrogen peroxide neutralizing compounds.
There continues to be a need for a one step contact lens disinfecting, and preferably cleaning, system using a hydrogen peroxide destroying component. The delayed release coating on tablets used in such systems should be of sufficient thickness and uniformity to allow enough time for lens disinfecting to take place while, at the same time, allowing release of the hydrogen peroxide destroying component in a reasonable period of time so that the disinfected lens can be safely and comfortably worn.